She said she had always been thin and wanted to know how to gain weight in a healthy way.

"In year 7, I was a stick. I had no muscle or fat and I really wanted to be more than that because I had no endurance for running," Amber said.

"I noticed there was no help anywhere and I asked my friends if they thought it was a good idea to create an app for people in my situation. We wanted to create an app to help people gain weight or loose weight or just get more fit.

"The hardest part of the competition was getting all the information organised and presenting it in a way that people would understand.

"It was nerve-wracking presenting our pitch, but it was pretty cool to hear that the judges loved our idea," she said.

The winning prize consisted of $200 to help develop the app, business coaching from entrepreneur Chris Mills and ongoing mentoring from Startup Toowoomba.

Amber said she could not wait to get the app developed.

"The next step is developing the app and get it up and running," Amber said.

"The whole experience was amazing. I would definitely encourage other people to take part because it's a great experience.

"It's a really good way to get started," she said.

Startup Toowoomba cofounder Leanne Griffin said the idea was fantastic.

"To be able to successfully validate your ideas and to present them in the way the girls did isn't easy," Ms Griffin said.

"They put together an excellent pitch. It was very polished and well thought out.

"They even have a website and a Facebook page," she said.

The girls already have hundreds of likes on their Facebook page and Amanda said it gave them confidence their app would be a success.

"It's unbelievable that we had more than 100 likes in 12 hours and now we are up around 300 in such a short time," she said.